Elastomeric thermoplastic gels are materials characterized by a very low hardness, elastic behaviour, i.e., they regain their initial shape after deformation, even to a considerable extent of deformation, and a softening temperature beyond which they become plastic, which facilitates their application.
Such gels can notably have a matrix of styrene thermoplastic elastomers (called “TPS”) such as the block copolymers styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS), styrene/butadiene/isoprene/styrene (SBIS), styrene/isobutylene/styrene (SIBS), styrene/ethylene/butylene/styrene (SEBS), styrene/ethylene/propylene/styrene (SEPS), styrene/ethylene/ethylene/propylene/styrene (SEEPS) and blends of these copolymers.
To achieve very low hardness, these gels also contain a high proportion of extender oils.
These gels can be prepared in two stages. In the first stage, the various constituents of the gel are fed, for example, into an extruder, which plasticates the thermoplastic elastomer and mixes it with an extender oil and any other desired additives. At the extruder's outlet, the plastic material is extruded for example into a rod, which is chopped to produce pellets or granules. To facilitate cooling of the plastic material, US Patent Application Publication 2002/0049276 states that extrusion and chopping of the rod can be carried out in water.
The granules or pellets can be stored. They are then reprocessed and injected into a mould to obtain their final forms.
However, this two-stage method of manufacture requires the use of antisticking agents to prevent the granules or pellets from sticking together. These antisticking agents have the drawback that they increase the hardness of the gels considerably.
PCT patent application publication WO 97/09391 proposes production of adhesives comprising a support and a thick elastomeric thermoplastic gel by extruding the plastic gel directly onto a support moving in translation. This manner of application can be used when the form ratio of the extrudate is close to one. This is no longer the case when it is desirable to obtain a flat profiled element, i.e., for which the thickness is much less than the width, and with controlled dimensions. It has been found that the low-viscosity plastic state of the material leaving the extruder die, i.e., the extrudate, and its very strong adhesiveness or stickiness, do not allow sufficient control of the dimensions of the flat profiled element in such an application.
U.S. Pat. No. 1,740,029 proposes a method and a device for extruding a rubber-like tube for the manufacture of inner tubes, in which the material leaving the extruder die is received on the surface of a water bath intended for cooling it without deforming it and without allowing its surface to vulcanize. In this device, the axis of the extruder die is horizontal.